SOME MAMMALIAN TAPEWORMS. 629 



the scolex appeal's to be of an oval contour, passing thus grarlually 

 into a neck, wliich is at first narrow and later widens out. There 

 is nothing abnormal about the shape of such a scolex. A close 

 examination, however, shows that such a description would be 

 quite incorrect. For the scolex itself is in I'eality almost semi- 

 circular in outline, and its outlines are carried on on either side 

 by the neck of the worm, which is, to begin with, rather wider 

 even than the thickest part of the scolex. This is clearly to be 

 seen in text-fig. 149. It seems to be imbedded in the first seg- 

 ments of the stroljila, like an egg in an egg-cup. Thus the true 

 scolex is very shoit. The widening of tlie strobila, for a space of 

 some five or six pi'oglottides, suggests the commencing formation 

 of a " pseudoscolex," such as is further developed in, for example, 

 Thysanocephalum crisjnwi *. 



The first steps in the formation of a pseudoscolex might well be 

 imagined to occur in some such way as is shown in the anterior 

 proglottides of the present species. There is, however, no fuither 

 indication of the formation of a pseudoscolex. The anterior pro- 

 glottides are precisely like those which follow, save in their 

 greater diameter. The figure also suggests that the scolex is 

 retractile within the first part of the strobila. In a sense this 

 is the case. Longitudinal sections through the scolex and tlie 

 commencing strobila show a bulging of the latter. There is a 

 plain demarcation between scolex and strobila, and not much 

 curving back of the anterior proglottides when thus viewed. 

 That the scolex itself may be extended to a gi-eater length is 

 possible enough. And yet in seven or eight examples which I 

 examined there was an identity of structure in this and other 

 particulars. It is to be noted, therefore, that this species, 

 unlike Oochoristica tetragonoce'phala, has no neck f, as, indeed, 

 was asserted of the latter by Diesing, but denied later by Liihe 

 and Janicki. 



In examining the scolex mounted entire, aftei- clearing with oil 

 of cloves or in alcohol previous to mounting, the suckers are by 

 no means so conspicuous as in other Tapeworms. The slit-like 

 orifice can, indeed, be detected, but it is rather shiouded and dim. 

 The reason for this is appaient when the scolex is studied by 

 means of transverse sections, in which the relations to the head 

 are shown. It will be there seen that, except for the small 

 orifice of the sucker, that organ is not by any means entirely 

 external in situation ; the sucker is, in fact, covered by a thickish 

 layer of the ordinaiy parenchyma of the body. It is thus imbedded 

 in the head, and represents a still further pronounced sessile 

 condition of the sucker, which {inter alia) distinguishes the 

 Teti'acotylea from the Tetraphyllidia. At the same time, the 

 sucker retains its cup-like form, the two edges although in 



* Cf. Benham in pt. iv. of 'A Treatise on Zoology,' ed. Sir E. Ray Lankester, 

 p. 121, lig. xvii. 2. 



f Unless, indeed, the anterior bulging part of the body of the worm is the neck. 

 But as it shows transverse furrows (text-tig. 149) I do not think that this is the case. 



